1. Technical Field
The present invention relates to a cutter and to a printer having a cutter wherein the bottom edge of the paper exit from which the cut-off ends of recording medium (the cut paper) are discharged is a substantially horizontal surface. More specifically, the invention relates to a cutter and to a printer having a cutter from which the cut-off portions can be discharged after cutting without accumulating at the paper exit.
2. Related Art
Printers that print on recording paper such as roll paper or label paper commonly have a cutter for cutting off the printed portion of the recording paper after printing is completed. The cutter is located at a position on the downstream end part in the transportation direction of the transportation path that passes from the printing position of the print head to the paper exit, and the cut-off portion that is cut off from the recording paper is discharged from the paper exit. Cutters include both scissor cutters that cause a movable knife to pivot in a scissor action to and away from a fixed knife, and guillotine cutters in which the movable knife moves bidirectionally in a straight line to and away from the fixed knife.
A scissor type paper cutter that can be disposed in a printer is taught in Japanese Unexamined Patent Appl. Pub. JP-A-H09-19890. In the cutter taught in JP-A-H09-19890 the fixed knife is disposed with the cutting edge facing up, and the movable knife pivots on a support pin at one end in the cutting direction of the movable knife between a standby position where a specific gap is formed between the cutting edge of the movable knife and the cutting edge of the fixed knife, and a cutting-completed position where the cutting edge of the movable knife and the cutting edge of the fixed knife overlap throughout the entire range of the cutting direction. The paper is inserted on the paper path from the fixed knife side and the cut-off portion is discharged from the movable knife side.
The paper exit disposed to the cutter or a printer with a cutter must have a narrow opening so that foreign matter is not inserted from the outside, and is generally long and narrow in the cutting direction (the paper width direction). More specifically, the bottom edge of the paper exit is commonly positioned slightly below the cutting edge of the fixed knife and the top edge of the paper exit is positioned slightly above the cutting edge of the fixed knife so that the vertical size of the opening is reduced. When the movable knife moves toward the cutting-completed position with this configuration, however, the upstream side end part in the paper discharge direction (transportation direction) of the cut-off portion is pushed below the bottom edge of the paper exit by the downward moving movable knife. The cut-off portion also becomes curled. As a result, when the movable knife returns to the standby position, the cut-off portion may spring up as a result of the resilience of the paper when the paper returns from the curled position.
To prevent the cut-off portion from being pushed down or popping out from the paper exit, the bottom edge of the paper exit may have a substantially level stage surface that extends for a specific width in the cutting direction along the edge of the fixed knife slightly below the cutting edge of the movable knife at the cutting-completed position. Because the stage surface that determines the bottom edge of the paper exit in this configuration is positioned below the cutting edge of the movable knife at the cutting-completed position, the movable knife does not push the upstream end part of the cut-off portion down when cutting, the upstream end part of the cut-off portion is above the bottom edge of the paper exit and is not caused to curl.
However, when the bottom edge of the paper exit is defined by a stage surface, the discharged cut-off portions can easily be left on the stage and collect in a pile when the roll paper inserted between the fixed knife and the movable knife is repeatedly cut into particularly short lengths. When the cut-off portions collect between the fixed knife and the movable knife, the accumulated cut-off portions interfere with the movable knife, preventing the movable knife from moving to the cutting-completed position and causing defective cuts. The movable knife can also bite into the cut-off portions and become unable to move, that is, become locked.